Hidden black hole could rewrite Milky Way's story
Astronomers have discovered a rare intermediate-mass black hole (IMBH) in the Milky Way galaxy, specifically at the center of Omega Centauri. This densely packed star cluster is located approximately 17,000 light-years away from Earth. The black hole's mass is equal to at least 8,200 Suns, positioning it within the mass range between star-mass black holes and supermassive black holes.
What did the scientists see?
The discovery was led by Maximilian Haberle of the Max Planck Institute for Astronomy in Germany. Haberle and his team saw seven fast-moving stars in the central region of Omega Centauri. He stated, "These stars' velocities were significantly higher than expected for the star cluster's central escape velocity," indicating a massive black hole's presence.
Role of IMBHs in understanding cosmic phenomena
IMBHs, like the one discovered, are relatively rare and fall within a poorly defined mass range. They serve as a 'connective tissue' between star-mass black holes and supermassive ones. Astronomers believe that supermassive black holes gradually grow from the slow accumulation and hierarchical mergers of stellar-mass black holes, but more evidence for IMBHs is required to account for the number of supermassive black holes observed.
Stellar kinematics key to black hole discovery
The discovery was facilitated by studying stellar kinematics, the movement of stars around a mass because of gravitational interactions. The team utilized 20 years of data from the Hubble Space Telescope, to construct an updated catalog of Omega Centauri's central region. They identified some fast-moving stars whose velocity and motion suggested they were interacting with a giant invisible mass, later confirmed as the IMBH.
